Using Serum Progesterone to Diagnose Ectopic Pregnancy
ABSTRACT & COMMENTARY
Source: Valley VT, et al. Serum progesterone and endovaginal sonography by emergency physicians in the evaluation of ectopic pregnancy. Acad Emerg Med 1998;5:309-313.
Valley and associates designed a prospective observational study to investigate the use of serum progesterone (SP) as an aid in the diagnosis of ectopic pregnancy (EP). They used a convenience sample model to explore the issue of a SP discriminatory level in ED patients with a positive pregnancy test and no definite intrauterine pregnancy (IUP) on ultrasound (US). The study, performed in an urban teaching hospital with an EM residency, covered a three-year period and enrolled patients with a positive pregnancy test and any of the following: pelvic/abdominal pain, vaginal bleeding, orthostasis, adnexal mass/tenderness, or risk factor for EP; unstable patients were excluded. Final diagnoses were tabulated. Endovaginal US was performed by emergency physicians; patients without definite IUP had a serum beta-HCG and SP measured. Post-hoc analysis of the SP relative to the US findings and final diagnoses was performed to determine the discriminatory SP value. They assumed a discriminatory zone of 2000 mlU/mL beta-HCG for endovaginal US in the detection of IUP.
Three hundred patients were studied with the following US findings: 169 IUP, 30 abnormal IUP, five EP, and 95 without IUP. Of patients without an IUP on US, the mean SP values were: normal IUP 22.8, spontaneous abortion 6.5, and ectopic pregnancy 7.5. The mean SP values were statistically different for normal IUP vs. abnormal pregnancy; no significant difference was found between SP values for EP and spontaneous abortion. Valley et al conclude that while no SP value can exclude an EP, a low SP (less than 11) in the setting of an endovaginal US without IUP suggests an abnormal pregnancy.
COMMENT BY WILLIAM BRADY, MD
This study revisits an alternative approach for the emergency physician to use in the evaluation of the patient with possible EP. Unfortunately, it does not answer the questions by providing a yes or no answer for the clinician. A low SP, however, in the risk factor-laden patient with the correct presentation for EP and a positive pregnancy test, with no demonstrable IUP on ultrasound, strongly suggests the diagnosis.
Two concerns include the practical application of such an approach to daily patient care, as well as the study design itself. Timeliness of the SP result from the clinical laboratory would obviously affect its usefulness. The SP laboratory technique, a radioimmunoassay, requires approximately four hours for completion; further, many hospitals do not possess the capability for such testing-rapid or otherwise. Valley et al did not report beta-HCG findings other than to state that the ". . .discriminatory zone of 2000 mlU/mL beta-HCG was selected." The discriminatory zone, in this instance, refers to the level at which an IUP would be apparent by endovaginal US. Many emergency physicians use the findings of both the quantitative beta-HCG and the US to determine both the need for obstetric consultation as well as disposition. The addition of this information to the study would be beneficial.
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